This application is related to magnetic recording techniques, devices, and systems.
Magnetic recording traditionally uses a longitudinal recording method where a recording medium is configured to have its anisotropy easy axes along the longitudinal directions within the magnetic recording medium plane. The storage density based on this method is known to be limited due to the thermal instability of the magnetic grains. An improved method based on a perpendicular recording configuration has been developed to mitigate some technical limitations in the longitudinal recording devices, e.g., to achieve better thermal stability than the longitudinal recording. Typically, a perpendicular recording configuration uses media with their medium anisotropy easy axes perpendicular to the medium plane and a single pole head with a soft magnetic under layer to enhance the write field. Another magnetic recording technique called “tilted longitudinal recording” has also been developed to use an inductive head with a tilted medium.
These recording techniques, however, have difficulties to address various limitations or barriers for further increasing the storage densities, such as the thermal stability issue, the medium noise, the bit error rate limitations, and the limited data rate due to the limited medium switching speed and other limitations. The thermal stability issue is particularly limiting in the longitudinal recording. The large media switching field distribution and transition width can lead to certain limitations in the perpendicular recording in addition to the limitation due to the media switching speed problem. In both longitudinal and perpendicular recording, the write field decreases with track width and this aspect of such methods limits the storage densities. Furthermore, the fringing field and the erase of neighboring tracks in both longitudinal and perpendicular recording are also barriers to achieving high storage densities.